[lld][ELF] Resolve Symbols with same comdat index as Defined Symbols

Author: pranav

lld/ELF/InputFiles.cpp

@@ -1756,13 +1756,22 @@ static void createBitcodeSymbol(Ctx &ctx, Symbol *&sym,
     sym = ctx.symtab->insert(objSym.getName());
   }
 
-  int c = objSym.getComdatIndex();
-  if (objSym.isUndefined() || (c != -1 && !keptComdats[c])) {
+  if (objSym.isUndefined()) {
     Undefined newSym(&f, StringRef(), binding, visibility, type);
     sym->resolve(ctx, newSym);
     sym->referenced = true;
     return;
   }
+  int c = objSym.getComdatIndex();
+  if (c != -1 && !keptComdats[c]) {
+    Defined newSym(ctx, &f, StringRef(), binding, visibility, type, 0, 0,
+                   nullptr);
+    if (objSym.canBeOmittedFromSymbolTable())
+      newSym.exportDynamic = false;
+    sym->resolve(ctx, newSym);
+    sym->referenced = true;
+    return;
+  }
 
   if (objSym.isCommon()) {
     sym->resolve(ctx, CommonSymbol{ctx, &f, StringRef(), binding, visibility,

lld/test/ELF/lto/comdat-weakodr-linkonceodr-visibility.ll

@@ -0,0 +1,36 @@
+; RUN: rm -rf %t.dir
+; RUN: split-file %s %t.dir
+; RUN: cd %t.dir
+; RUN: echo %t.dir
+; RUN: llvm-as explicit.ll -o explicit.bc
+; RUN: llvm-as implicit.ll -o implicit.bc
+
+
+;; Case 1:
+; RUN: ld.lld explicit.bc implicit.bc -o case1.so -shared -save-temps
+; RUN: llvm-nm case1.so.0.2.internalize.bc | FileCheck %s
+
+;; Case 2:
+; RUN: ld.lld implicit.bc explicit.bc -o case2.so -shared -save-temps
+; RUN: llvm-nm case2.so.0.2.internalize.bc | FileCheck %s
+
+; CHECK: W foo
+
+;--- explicit.ll
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+$foo = comdat any
+define weak_odr void @foo() local_unnamed_addr comdat {
+  ret void
+}
+
+
+;--- implicit.ll
+target triple = "x86_64-unknown-linux-gnu"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+$foo = comdat any
+define linkonce_odr void @foo() local_unnamed_addr comdat {
+  ret void
+}